Plasma display panel (PDP) is a display panel which displays images by generating gas discharge in a discharge space called a cell in which a discharge gas such as rare gas to excite a phosphor by vacuum ultra violet rays generated by the gas discharge.
Currently, generally commercialized PDPs employing an AC (alternate current) driving method are surface discharge type. The surface discharge type PDP can arrange phosphors for color display away from display electrode pairs toward a thickness direction of the panel, and characteristic degradation of the phosphors due to ion bombardment (sputtering) in discharge can be accordingly reduced. Therefore, the surface discharge type PDP is suitable for elongating lifetime as compared with an opposed discharge type PDP in which display electrodes to be paired (called an X electrode and a Y electrode) are distributed to a front plate and a rear plate.
In the generally used surface discharge type PDPs, a protective film for preventing a dielectric layer from degradation due to ion bombardment in discharge is provided to a front plate. The protective film not only prevents the dielectric layer from degradation due to ion bombardment in discharge, but also has a function to grow discharge by emitting secondary electrons as ions collide against the protective film.
As the protective film, a thin film of magnesium oxide (MgO) is generally used according to its ion bombardment resistance and easiness in secondary electron emission (refer to Japanese Patent Application Laid-Open Publication No. 2006-147417 (Patent Document 1)).